A084199 Smallest prime q < prime(n) such that q+1 divides prime(n)+1, a(n) = 1 if no such q exists.

1, 1, 2, 3, 2, 1, 2, 3, 2, 2, 3, 1, 2, 3, 2, 2, 2, 1, 3, 2, 1, 3, 2, 2, 13, 2, 3, 2, 1, 2, 3, 2, 2, 3, 2, 3, 1, 3, 2, 2, 2, 13, 2, 1, 2, 3, 3, 3, 2, 1, 2, 2, 1, 2, 2, 2, 2, 3, 1, 2, 3, 2, 3, 2, 1, 2, 3, 1, 2, 13, 2, 2, 3, 1, 3, 2, 2, 1, 2, 1, 2, 1, 2, 13, 3, 2, 2, 1, 2, 3, 2, 2, 3, 2, 3, 2, 2, 2, 3, 1, 3, 2, 2

Offset

1,3

Comments

Conjecture: A008578 is the range of values (or A000040 = range of values > 1).

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = 1 iff A084196(n) = 0.

Mathematica

seq[lim_] := Module[{p = Prime[Range[lim]], q, s = {}}, Do[q = SelectFirst[p, Divisible[p[[i]] + 1, # + 1] &]; AppendTo[s, If[q < p[[i]], q, 1]], {i, 1, Length[p]}]; s]; seq[100] (* Amiram Eldar, Mar 28 2025 *)

Crossrefs

Cf. A000040, A008578, A084196.

Sequence in context: A068073 A324504 A032452 * A277745 A353497 A320858

Adjacent sequences: A084196 A084197 A084198 * A084200 A084201 A084202

Keyword

nonn

Author

Reinhard Zumkeller, May 18 2003

Status

approved